title: Temperature-dependent Raman study of a CeFeAsO(0.9)F(0.1) superconductor: crystal field excitations, phonons and their coupling.
abstract: We report temperature-dependent Raman spectra of CeFeAsO(0.9)F(0.1) from 4 to 300 K in the spectral range of 60-1800 cm(-1) and interpret them using estimates of phonon frequencies obtained from first-principles density functional calculations. We find evidence for strong coupling between the phonons and crystal field excitations; in particular the Ce(3 + ) crystal field excitation at 432 cm(-1) couples strongly with the E(g) oxygen vibration at 389 cm(-1). Below the superconducting transition temperature, the phonon mode near 280 cm(-1) shows softening, signaling its coupling with the superconducting gap. The ratio of the superconducting gap to T(c), thus estimated to be ~10, suggests CeFeAsO(0.9)F(0.1) to be a strong coupling superconductor. In addition, two high frequency modes observed at 1342 and 1600 cm(-1) are attributed to electronic Raman scattering from the (x(2)-y(2)) to xz /yz d-orbitals of Fe.
authors.affiliation: Department of Physics, Indian Institute of Science, Bangalore, India.
authors.forename: Pradeep
authors.initials: P
authors.lastname: Kumar
authors.forename: Anil
authors.initials: A
authors.lastname: Kumar
authors.forename: Surajit
authors.initials: S
authors.lastname: Saha
authors.forename: D V S
authors.initials: DV
authors.lastname: Muthu
authors.forename: J
authors.initials: J
authors.lastname: Prakash
authors.forename: U V
authors.initials: UV
authors.lastname: Waghmare
authors.forename: A K
authors.initials: AK
authors.lastname: Ganguli
authors.forename: A K
authors.initials: AK
authors.lastname: Sood